Combat solders, law enforcement personnel, and others exposed to potential dangerous situation, the ready availability of information is essential in all environmental conditions. A Night Vision Device (NVD) is an optical instrument for producing images in levels of light approaching total darkness. NVD usually refers to a complete unit, including an image intensifier tube, a protective and generally water-resistant housing, and a mounting system. Many NVDs also include sacrificial lenses, IR illuminators, and telescopic lenses. Night vision systems can be hand-held, weapon mounted, or helmet mounted for easy operation.
Low-light imaging, near-infrared illumination and thermal imaging are the common methods for achieving Night Vision. The most common applications of night vision systems are situational awareness, target cueing, night driving or flying, night security and surveillance, wildlife observation, sleep lab monitoring and search and rescue.
Low-light imaging uses a device called an image intensifier to amplify available light to achieve better vision. The available light is focused through the objective lens onto a photocathode of the image intensifier. Then the electrons released by the cathode are accelerated by an electric field. The accelerated electrons enter holes in a microchannel plate and bounce off specially-coated internal walls which generate more electrons as they bounce through. This activity creates a denser “cloud” of electrons representing an intensified version of the original image. The electrons hit a phosphor screen, making the phosphor glow. The light displays the desired view to the user or to an attached camera or video device. In low light imaging, user cannot see through smoke and heavy sand storms and cannot see a person hidden under camouflage. In near-infrared illumination method, a device that is sensitive to invisible near infrared radiation is used in conjunction with an infrared illuminator. The method of near-infrared illumination has been used in a variety of night vision applications including perimeter protection.
Thermal imaging night vision methods do not require any ambient light and operate on the principal that all objects emit infrared energy as a function of their temperature. In general, the hotter an object is, the more radiation it emits. A thermal imager is a product that collects the infrared radiation from objects in the scene and creates an electronic image. Since they do not rely on reflected ambient light, thermal imagers are entirely ambient light-level independent. In addition, they also are able to penetrate obscurants such as smoke, fog and haze. The thermal images show the targets as black or white, depending upon the object temperature. Infrared thermal imaging is less attenuated by smoke and dust and a drawback is that they do not have sufficient resolution and sensitivity to provide acceptable imagery of a scene.
Digital Night Vision (DNV) systems are well known for Situational Awareness (SA) and target cueing and are widely used in military applications. Fusion systems have been developed that combine low light level imaging with thermal imaging. The low light level imaging information and thermal imaging information are fused to obtain a fused image that provides advantages of both thermal and low light imaging. In such systems low light level imaging can be utilized for SA and thermal imaging can be utilized for target cueing.
The fused DNV systems utilizes the RGB color channels to distinguish SA information in green and target cueing information in red. As shown in FIG. 1, conventional fused man-portable systems 100, directly map the thermal sensor 102 to threat detection (target cueing) 106 and the (Low light Level) LLL sensor 104 to the SA channel 108. As a result, in extremely low light “dark cave” situations, the LLL sensor 104 cannot provide SA information, as the user is blind to the surroundings. In case of situational awareness, it is found that resolution tends to deteriorate below overcast starlight. Also, in case of threat detection and target cueing, there can also be reduced threat cueing in all conditions. In such conventional fused man-portable systems, the threshold of thermal data is fixed. In dark scenarios, such as low Signal to Noise Ratio (SNR) on low light sensor, the thermal data below the threshold is disgraded and the SA is limited by low level sensor resolution.
None of the existing technologies provides situational awareness for the user in a range of conditions from low light to no light situations. Therefore, it is believed that a need exists for an improved system and method for situational awareness capability that surpasses any existing low light level sensor technology in a single channel (stand-alone) application in overcast star light and below conditions. Further such system and method should provide situational awareness that never drops below the native resolution of the thermal sensor.